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Evolution, Medicine, and Public Health [2015] pp. 193–194
emph clinical briefs:
foundational
doi:10.1093/emph/eov018
Horizontal Gene Transfer
Alita R. Burmeister1,2,3
1
Department of Microbiology and Molecular Genetics, 2Department of Ecology, Evolutionary Biology, and Behavior Program,
and 3BEACON Center for the Study of Evolution in Action, Michigan State University
DEFINITION AND BACKGROUND
Horizontal gene transfer (HGT) is the
movement of genetic information between
organisms, a process that includes the
spread of antibiotic resistance genes
among bacteria (except for those from parent to offspring), fueling pathogen
evolution.
Many resistance genes evolved long
ago in natural environments with no anthropogenic influence but these genes are
now rapidly spreading to and among
human pathogens. HGT occurs by three
well-understood genetic mechanisms
(Fig. 1):
. Transformation:
Bacteria take up
DNA from their environment
. Conjugation: Bacteria directly transfer genes to another cell
. Transduction: Bacteriophages (bacterial viruses) move genes from
one cell to another
EXAMPLES IN HUMAN BIOLOGY
AND PUBLIC HEALTH
EXAMPLES IN CLINICAL
MEDICINE
Antibiotic use in human medicine and agriculture continually selects for resistant bacteria [2, 6]. For example, tetracycline and lactams commonly fed to animals provide
a selective environment for tetracycline and
methicillin resistance. Genes conferring
resistance to these antibiotics have horizontally transferred into a sensitive
human-associated Staphylococcus aureus
strain, resulting in methicillin-resistant
strain CC398 [7]. After a strain gains resistance by HGT, the bacteria proliferate and
continue to evolve as they move among patients and hospitals [1]. This process
occurs in many bacterial lineages, resulting
in diverse populations of a variety of
strains, such as USA300 [5].
Ongoing HGT poses a problem for clinical
surveillance and treatment. Bacterial populations evolve rapidly, resulting in diversity
that necessitates individual screening to
determine effective treatments and to detect new strains, such as methicillin and
high level vancomycin resistant S.aureus
(MRSA and VRSA) [2]. Even when new
drugs and diagnostic tools become available, the persistence of HGT will require
ongoing surveillance for newly resistant
pathogens, leaving practitioners and researchers racing with evolution.
funding
This material is based upon work supported by the
National Science Foundation Graduate Research
Fellowship Program under Grant No. DGE1424871.
Once transferred, the genes and pathogens
continue to evolve, often resulting in
bacteria with greater resistance [1, 2, 3, 4].
All genes—not just those causing drug resistance—may be horizontally transferred
and proliferate by natural selection,
including virulence determinants [5].
references
1. Harris SR, Feil EJ, Holden MTG et al. Evolution of
MRSA during hospital transmission and intercontinental spread. Science 2010;327:469–74.
2. Lindsay, J. A. Hospital-associated MRSA and
antibiotic resistance-what have we learned from
genomics? Int J Med Microbiol 2013;303:318–23
3. McCarthy AJ, Loeffler A, Witney AA et al.
Extensive horizontal gene transfer during
Staphylococcus aureus co-colonization in vivo.
Genome Biol Evol 2014;6:2697–708.
4. Stanczak-Mrozek KI, Manne A, Knight GM et al.
Figure 1. Mechanisms of bacterial horizontal
Within-host diversity of MRSA antimicrobial
gene transfer
resistances. J Antimicrob Chemother 2015;70:
2191–2198.
5. McDougal LK, Steward CD, Killgore GE et al.
Pulsed-field gel electrophoresis typing of oxacillin-resistant Staphylococcus aureus isolates
ß The Author(s) 2015. Published by Oxford University Press on behalf of the Foundation for Evolution, Medicine, and Public Health.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and
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6. US Department of Health and Human Services.
7. Price LB, Stegger M, Hasman H et al.
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Staphylococcus aureus CC398: host adaptation
Atlanta: CDC, 2013; p, 11–14.
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